Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$163.80	4.684%	$171.4724	$171.47	$171.45	$171.50
Purchase #2	$93.69	7.373%	$100.5978	$100.60	$100.60	$100.60
Purchase #3	$129.49	6.476%	$137.8758	$137.88	$137.90	$137.90
Purchase #4	$142.64	3.667%	$147.8706	$147.87	$147.85	$147.90
Purchase #5	$203.52	6.435%	$216.6165	$216.62	$216.60	$216.60
Purchase #6	$14.46	6.821%	$15.4463	$15.45	$15.45	$15.40
Purchase #7	$176.73	9.789%	$194.0301	$194.03	$194.05	$194.00
7 purchase totals =	$924.33		$983.9095	$983.92	$983.90	$983.90